The present invention relates to all terrain vehicles (ATV) and, in particular, to a drive train suspension for a vehicle having multiple pivot axes to permit independent longitudinal and transverse pivoting of the frame suspension and supported tracks and/or wheels.
A wide variety of all terrain vehicles have been developed for travel over off-road terrain of all types and including rocks, bog, rivers, sand, snow and ice. These vehicles typically include flexible suspensions that support floatation tires and/or tracks to produce relatively low pounds per square inch (psi) footprints to minimize incapacitating the vehicle.
Vehicles are also known wherein interconnecting members or beams of associated suspension frames are coupled together to pivot relative to each other independent of the vehicle operator compartment. As supported wheels or tracks encounter obstructions, the pivot joints allow the suspension frame to flex independent of the suspension members securing the wheels to the vehicle. A term sometimes used to describe a frame suspension of the foregoing type s is a “walking beam” suspension but which typically are believed to provide a single pivot.
The present invention was developed to provide an improved multi-pivot vehicle frame suspension that permits a support frame for several included wheels and/or tracks to independently flex and accommodate relatively severe terrains. In various vehicle constructions, the vehicle provides frame suspensions with five and eight pivot points of differing pivot constructions that independently pivot from four supported tracks. Each track assembly is independently supported to the multi-pivot suspension frame and includes a track framework that accommodates independent, torsion controlled track movement with encountered obstacles. The track assemblies are also mounted to independently pivot to accommodate front, rear, crab and 360° degrees steering at the track assemblies.
Each track assembly includes a framework having a drive portion containing a drive sprocket and an arcuate upper bearing support plate. The upper bearing support plate pivots clockwise and counter clockwise relative to an intervening slide bearing member and an arcuate lower bearing support plate. The lower bearing support plate separately supports sets of idler wheels or rollers of differing sizes from torsion biased rocker arms. A track trained around the drive sprocket and idler roller framework thereby independently flexes fore and aft to rise and fall and change shape as necessary to maintain contact with encountered obstacles.
The rocker arm assemblies are coupled to the track frame with axles fitted to collars containing elastomer shims that resist and bias axle rotation to an equilibrium position. Similar torsion couplers are used at the multi-pivot vehicle suspension frame. Alternative multi-pivot frame suspensions, track assemblies and improved internal, track drive lugs are disclosed. Critical edges of the drive lug are particularly chamfered to relieve wheel lug contact prevent the idler wheels from creeping upward along the lugs and derailing. Collectively, the vehicle frame and track assemblies independently rise and fall as obstacles of differing configurations and types are encountered, while maintaining the operator compartment substantially parallel to the ground.